using System;
using System.IO;
using System.Security.Cryptography;


namespace BTVPodcatcherNamespace
{
    //

    //    This sample code is provided "AS IS" with no warranties, and confers no rights.

    //

    //    ATTENTION: This sample is designed to be more of a tutorial rather than something

    //                you can copy and paste in the production code!

    //                See the topic on "making it industry strength" in the blog.

    //






    //

    // Sample encrypt/decrypt functions

    //    Parameter checks and error handling are ommited for better readability

    //

    public class EncDec
    {



        // Encrypt a byte array into a byte array using a key and an IV

        public static byte[] Encrypt(byte[] clearData, byte[] Key, byte[] IV)
        {

            // Create a MemoryStream that is going to accept the encrypted bytes

            MemoryStream ms = new MemoryStream();



            // Create a symmetric algorithm.

            // We are going to use Rijndael because it is strong and available on all platforms.

            // You can use other algorithms, to do so substitute the next line with something like

            //                      TripleDES alg = TripleDES.Create();

            Rijndael alg = Rijndael.Create();



            // Now set the key and the IV.

            // We need the IV (Initialization Vector) because the algorithm is operating in its default

            // mode called CBC (Cipher Block Chaining). The IV is XORed with the first block (8 byte)

            // of the data before it is encrypted, and then each encrypted block is XORed with the

            // following block of plaintext. This is done to make encryption more secure.

            // There is also a mode called ECB which does not need an IV, but it is much less secure.

            alg.Key = Key;

            alg.IV = IV;



            // Create a CryptoStream through which we are going to be pumping our data.

            // CryptoStreamMode.Write means that we are going to be writing data to the stream

            // and the output will be written in the MemoryStream we have provided.

            CryptoStream cs = new CryptoStream(ms, alg.CreateEncryptor(), CryptoStreamMode.Write);



            // Write the data and make it do the encryption

            cs.Write(clearData, 0, clearData.Length);



            // Close the crypto stream (or do FlushFinalBlock).

            // This will tell it that we have done our encryption and there is no more data coming in,

            // and it is now a good time to apply the padding and finalize the encryption process.

            cs.Close();



            // Now get the encrypted data from the MemoryStream.

            // Some people make a mistake of using GetBuffer() here, which is not the right way.

            byte[] encryptedData = ms.ToArray();



            return encryptedData;

        }





        // Encrypt a string into a string using a password

        //    Uses Encrypt(byte[], byte[], byte[])

        public static string Encrypt(string clearText, string Password)
        {

            // First we need to turn the input string into a byte array.

            byte[] clearBytes = System.Text.Encoding.Unicode.GetBytes(clearText);



            // Then, we need to turn the password into Key and IV

            // We are using salt to make it harder to guess our key using a dictionary attack -

            // trying to guess a password by enumerating all possible words.

            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,

                        new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });



            // Now get the key/IV and do the encryption using the function that accepts byte arrays.

            // Using PasswordDeriveBytes object we are first getting 32 bytes for the Key

            // (the default Rijndael key length is 256bit = 32bytes) and then 16 bytes for the IV.

            // IV should always be the block size, which is by default 16 bytes (128 bit) for Rijndael.

            // If you are using DES/TripleDES/RC2 the block size is 8 bytes and so should be the IV size.

            // You can also read KeySize/BlockSize properties off the algorithm to find out the sizes.

            byte[] encryptedData = Encrypt(clearBytes, pdb.GetBytes(32), pdb.GetBytes(16));



            // Now we need to turn the resulting byte array into a string.

            // A common mistake would be to use an Encoding class for that. It does not work

            // because not all byte values can be represented by characters.

            // We are going to be using Base64 encoding that is designed exactly for what we are

            // trying to do.

            return Convert.ToBase64String(encryptedData);



        }





        // Encrypt bytes into bytes using a password

        //    Uses Encrypt(byte[], byte[], byte[])

        public static byte[] Encrypt(byte[] clearData, string Password)
        {

            // We need to turn the password into Key and IV.

            // We are using salt to make it harder to guess our key using a dictionary attack -

            // trying to guess a password by enumerating all possible words.

            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,

                        new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });



            // Now get the key/IV and do the encryption using the function that accepts byte arrays.

            // Using PasswordDeriveBytes object we are first getting 32 bytes for the Key

            // (the default Rijndael key length is 256bit = 32bytes) and then 16 bytes for the IV.

            // IV should always be the block size, which is by default 16 bytes (128 bit) for Rijndael.

            // If you are using DES/TripleDES/RC2 the block size is 8 bytes and so should be the IV size.

            // You can also read KeySize/BlockSize properties off the algorithm to find out the sizes.

            return Encrypt(clearData, pdb.GetBytes(32), pdb.GetBytes(16));



        }





        // Encrypt a file into another file using a password

        public static void Encrypt(string fileIn, string fileOut, string Password)
        {

            // First we are going to open the file streams

            FileStream fsIn = new FileStream(fileIn, FileMode.Open, FileAccess.Read);

            FileStream fsOut = new FileStream(fileOut, FileMode.OpenOrCreate, FileAccess.Write);



            // Then we are going to derive a Key and an IV from the Password and create an algorithm

            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,

                        new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });



            Rijndael alg = Rijndael.Create();



            alg.Key = pdb.GetBytes(32);

            alg.IV = pdb.GetBytes(16);



            // Now create a crypto stream through which we are going to be pumping data.

            // Our fileOut is going to be receiving the encrypted bytes.

            CryptoStream cs = new CryptoStream(fsOut, alg.CreateEncryptor(), CryptoStreamMode.Write);



            // Now will will initialize a buffer and will be processing the input file in chunks.

            // This is done to avoid reading the whole file (which can be huge) into memory.

            int bufferLen = 4096;

            byte[] buffer = new byte[bufferLen];

            int bytesRead;



            do
            {

                // read a chunk of data from the input file

                bytesRead = fsIn.Read(buffer, 0, bufferLen);



                // encrypt it

                cs.Write(buffer, 0, bytesRead);



            } while (bytesRead != 0);



            // close everything

            cs.Close(); // this will also close the unrelying fsOut stream

            fsIn.Close();

        }







        // Decrypt a byte array into a byte array using a key and an IV

        public static byte[] Decrypt(byte[] cipherData, byte[] Key, byte[] IV)
        {

            // Create a MemoryStream that is going to accept the decrypted bytes

            MemoryStream ms = new MemoryStream();



            // Create a symmetric algorithm.

            // We are going to use Rijndael because it is strong and available on all platforms.

            // You can use other algorithms, to do so substitute the next line with something like

            //                      TripleDES alg = TripleDES.Create();

            Rijndael alg = Rijndael.Create();



            // Now set the key and the IV.

            // We need the IV (Initialization Vector) because the algorithm is operating in its default

            // mode called CBC (Cipher Block Chaining). The IV is XORed with the first block (8 byte)

            // of the data after it is decrypted, and then each decrypted block is XORed with the previous

            // cipher block. This is done to make encryption more secure.

            // There is also a mode called ECB which does not need an IV, but it is much less secure.

            alg.Key = Key;

            alg.IV = IV;



            // Create a CryptoStream through which we are going to be pumping our data.

            // CryptoStreamMode.Write means that we are going to be writing data to the stream

            // and the output will be written in the MemoryStream we have provided.

            CryptoStream cs = new CryptoStream(ms, alg.CreateDecryptor(), CryptoStreamMode.Write);



            // Write the data and make it do the decryption

            cs.Write(cipherData, 0, cipherData.Length);



            // Close the crypto stream (or do FlushFinalBlock).

            // This will tell it that we have done our decryption and there is no more data coming in,

            // and it is now a good time to remove the padding and finalize the decryption process.

            cs.Close();



            // Now get the decrypted data from the MemoryStream.

            // Some people make a mistake of using GetBuffer() here, which is not the right way.

            byte[] decryptedData = ms.ToArray();



            return decryptedData;

        }





        // Decrypt a string into a string using a password

        //    Uses Decrypt(byte[], byte[], byte[])

        public static string Decrypt(string cipherText, string Password)
        {

            // First we need to turn the input string into a byte array.

            // We presume that Base64 encoding was used

            byte[] cipherBytes = Convert.FromBase64String(cipherText);



            // Then, we need to turn the password into Key and IV

            // We are using salt to make it harder to guess our key using a dictionary attack -

            // trying to guess a password by enumerating all possible words.

            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,

                        new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });



            // Now get the key/IV and do the decryption using the function that accepts byte arrays.

            // Using PasswordDeriveBytes object we are first getting 32 bytes for the Key

            // (the default Rijndael key length is 256bit = 32bytes) and then 16 bytes for the IV.

            // IV should always be the block size, which is by default 16 bytes (128 bit) for Rijndael.

            // If you are using DES/TripleDES/RC2 the block size is 8 bytes and so should be the IV size.

            // You can also read KeySize/BlockSize properties off the algorithm to find out the sizes.

            byte[] decryptedData = Decrypt(cipherBytes, pdb.GetBytes(32), pdb.GetBytes(16));



            // Now we need to turn the resulting byte array into a string.

            // A common mistake would be to use an Encoding class for that. It does not work

            // because not all byte values can be represented by characters.

            // We are going to be using Base64 encoding that is designed exactly for what we are

            // trying to do.

            return System.Text.Encoding.Unicode.GetString(decryptedData);



        }





        // Decrypt bytes into bytes using a password

        //    Uses Decrypt(byte[], byte[], byte[])

        public static byte[] Decrypt(byte[] cipherData, string Password)
        {

            // We need to turn the password into Key and IV.

            // We are using salt to make it harder to guess our key using a dictionary attack -

            // trying to guess a password by enumerating all possible words.

            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,

                        new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });



            // Now get the key/IV and do the Decryption using the function that accepts byte arrays.

            // Using PasswordDeriveBytes object we are first getting 32 bytes for the Key

            // (the default Rijndael key length is 256bit = 32bytes) and then 16 bytes for the IV.

            // IV should always be the block size, which is by default 16 bytes (128 bit) for Rijndael.

            // If you are using DES/TripleDES/RC2 the block size is 8 bytes and so should be the IV size.

            // You can also read KeySize/BlockSize properties off the algorithm to find out the sizes.

            return Decrypt(cipherData, pdb.GetBytes(32), pdb.GetBytes(16));



        }





        // Decrypt a file into another file using a password

        public static void Decrypt(string fileIn, string fileOut, string Password)
        {

            // First we are going to open the file streams

            FileStream fsIn = new FileStream(fileIn, FileMode.Open, FileAccess.Read);

            FileStream fsOut = new FileStream(fileOut, FileMode.OpenOrCreate, FileAccess.Write);



            // Then we are going to derive a Key and an IV from the Password and create an algorithm

            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,

                        new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });



            Rijndael alg = Rijndael.Create();



            alg.Key = pdb.GetBytes(32);

            alg.IV = pdb.GetBytes(16);



            // Now create a crypto stream through which we are going to be pumping data.

            // Our fileOut is going to be receiving the Decrypted bytes.

            CryptoStream cs = new CryptoStream(fsOut, alg.CreateDecryptor(), CryptoStreamMode.Write);



            // Now will will initialize a buffer and will be processing the input file in chunks.

            // This is done to avoid reading the whole file (which can be huge) into memory.

            int bufferLen = 4096;

            byte[] buffer = new byte[bufferLen];

            int bytesRead;



            do
            {

                // read a chunk of data from the input file

                bytesRead = fsIn.Read(buffer, 0, bufferLen);



                // Decrypt it

                cs.Write(buffer, 0, bytesRead);



            } while (bytesRead != 0);



            // close everything

            cs.Close(); // this will also close the unrelying fsOut stream

            fsIn.Close();

        }







        



    }
}
